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INTRODUCTORY


  M. Simpson, wordsrmagic2me.com

AUTHORSHIP AND CITATION:
Gucker, Corey L. 2007. Pyrola asarifolia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/forb/pyrasa/all.html [].

Revisions: On 5 July 2017, the common name of this species was changed from: pink wintergreen
to: liverleaf wintergreen in FEIS.

FEIS ABBREVIATION:
PYRASA

NRCS PLANT CODE [83]:
PYAS
PYASA
PYASB2

COMMON NAMES:
liverleaf wintergreen
alpine wintergreen
pink shinleaf
pink wintergreen

TAXONOMY:
The scientific name of liverleaf wintergreen is Pyrola asarifolia Michx. (Pyrolaceae) [31,34].

Infrataxa:
Pyrola asarifolia Michx. subsp. asarifolia [17,28,31,34]
Pyrola asarifolia subsp. bracteata (Hook.) Haber [17,28,31,34]

Hybrids: Naturally occurring hybrids of liverleaf wintergreen largeflowered wintergreen (P. grandiflora) occur in British Columbia and the Yukon Territory [17]. Liverleaf wintergreen snowline wintergreen (P. minor) hybrid populations occur in Quebec, Ontario, Colorado, Alberta, British Columbia, Yukon, and Alaska [18].

SYNONYMS:
Pyrola asarifolia var. bracteata (Hook.) Jepson [57]=
   Pyrola asarifolia subsp. bracteata [34]

Pyrola asarifolia var. incarnata (DC.) Fern. [1,4,26]=
   Pyrola asarifolia subsp. asarifolia [34]

Pyrola asarifolia var. purpurea (Bunge) Fern. [30,33,42,57,64,89]=
   Pyrola asarifolia subsp. asarifolia [34]

Pyrola bracteata Hook. [46,63,70]=
   Pyrola asarifolia subsp. asarifolia [34]

Pyrola californica Krisa [56]=
   Pyrola asarifolia subsp. asarifolia [34]

Pyrola rotundifolia subsp. asarifolia (Michx.) A&D Lve [93,94]=
   Pyrola asarifolia subsp. asarifolia [34]

Pyrola uliginosa Torr. & Gray ex Torr. [6,7,70,81]=
   Pyrola asarifolia subsp. asarifolia [34]

LIFE FORM:
Forb

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Information on state-level protected status of plants in the United States is available at Plants Database.

DISTRIBUTION AND OCCURRENCE

SPECIES: Pyrola asarifolia
GENERAL DISTRIBUTION:
Liverleaf wintergreen is most common throughout Canada and the northern United States. However, in the western United States, liverleaf wintergreen occurs as far south as New Mexico and California. In the southwestern United States, liverleaf wintergreen is restricted to high-elevation habitats [1,28,35]. Pyrola asarifolia subsp. asarifolia is more widely distributed than P. a. subsp. bracteata and occupies the entire range described for liverleaf wintergreen. Pyrola asarifolia subsp. bracteata is restricted to the western United States and Canada. In the United States, P. a. subsp. bracteata does not occur farther east than Montana [83].

Plants Database provides a distributional map of liverleaf wintergreen and its subspecies.

HABITAT TYPES AND PLANT COMMUNITIES:
Liverleaf wintergreen is a small plant that rarely produces enough cover to be considered a community dominant. It often occurs in early seral deciduous forests dominated by poplar, birch, willow, and/or alder (Populus, Betula, Salix, Alnus spp.) that regenerate following canopy removal in coniferous forests. Liverleaf wintergreen persists as deciduous forests succeed to dense coniferous and/or boreal forest types. Overstory dominants in these forests include white spruce (Picea glauca), Sitka spruce (P. sitchensis), western redcedar (Thuja plicata), western hemlock (Tsuga heterophylla), Douglas-fir (Pseudotsuga menziesii), subalpine fir (Abies lasiocarpa), white fir (A. concolor), and lodgepole pine (Pinus contorta).

The following vegetation types and communities include liverleaf wintergreen as a dominant or differentiating species:

Colorado: British Columbia:

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Pyrola asarifolia

 

  Dave Powell, USDA Forest Service, www.forestryimages.org
GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [13,14,28,29,33]).

Aboveground description: Liverleaf wintergreen is an evergreen, glabrous, creeping perennial [1,30,57,61]. Nearly leafless flowering stalks are the tallest part of the plant [31]. Basal leaves are simple, alternate, and crowded in a rosette [31,35]. Blades are leathery, shiny, and circular to heart-shaped [33,61]. Leaf petioles are typically as long as the leaf blades [30,61]. Holmgren and others [31] report that leaf blades measure 0.8 to 4 inches (2-10 cm) long by 0.8 to 3 inches (2-8 cm) wide, and that petioles are 0.6 to 3.3 inches (1.5-8.5 cm) long. However, morphology is variable and affected by site conditions [17]. In western habitats leaf blades are generally wider than they are long, and in eastern habitats leaf blades are typically longer than they are wide. Leaves are often leathery in dry habitats and soft in wet habitats. Plants in moss hummocks often have particularly long, flexible petioles [17]. Liverleaf wintergreen, as the name implies, produces liverleaf to red-purple flowers, and flower color is often used in identification. Four to 25 nodding flowers occur in a loose raceme on stems up to 16 inches (40 cm) tall [1,17,31,61]. Flower stalks may have up to 3 scale leaves [13,14]. Liverleaf wintergreen fruits are 5-chambered rounded capsules [1,61]. Capsules measure 4 to 8 mm in diameter, contain numerous seeds, and open from the base [1,14,52].

Belowground description: Liverleaf wintergreen is rhizomatous. Rhizomes are shallow [16,30] and described as scaly, slender, long, branching, and extensive [14,17,61]. In jack pine (Pinus banksiana)-dominated stands in central Alberta, the maximum liverleaf wintergreen rooting depth was 7.1 inches (18 cm) [78].

Subspecies: A key for distinguishing P. a. subsp. asarifolia and P. a. subsp. bracteata is available [17].

RAUNKIAER [62] LIFE FORM:
Hemicryptophyte

REGENERATION PROCESSES:
Liverleaf wintergreen produces seeds and rhizomes. Information on seed production, seed dispersal, and seedling establishment was lacking as of 2007. Lackschewitz [42] reports that liverleaf wintergreen propagates by rhizomes. Studies of liverleaf wintergreen regeneration are needed.

Pollination: Because liverleaf wintergreen produces perfect flowers, self pollination is possible, but pollination strategies were not discussed in the available literature (2007).

Breeding system: Liverleaf wintergreen flowers are perfect [26].

Seed production and dispersal: The only studies of liverleaf wintergreen seed production, dispersal, and banking are summarized in seed banking.

Seed banking: Liverleaf wintergreen germinated from soils collected in tufted hairgrass/sedge (Deschampsia caespitosa/Carex spp.) meadows in the Greater Yellowstone ecosystem of Montana and Wyoming but not from soils collected in mixed forests in Oregon's central Cascade Range or from soils collected in quaking aspen (Populus tremuloides) woodlands in northeastern Alberta. Fifty-three liverleaf wintergreen seedlings/m emerged from seed in soils collected in unburned tufted hairgrass meadows. Almost double this number of seedlings emerged when unburned soil samples were heated to 120 F (50 C) for 1 hour. Emergence was about half as much when heated to 210 F (100 C) for 1 hour. There was no emergence from soils heated at 300 F (150 C) for 1 hour or from soils collected in burned meadows [4]. Additional information on this study is available in Fire Effects.

Liverleaf wintergreen was not collected in seed traps and did not germinate from soil samples collected in mixed forests or gravel bars in Oregon's central Cascade Range. In mixed forest sites, liverleaf wintergreen occurred with an average of 0.1% cover/m; liverleaf wintergreen was not present on vegetated or unvegetated gravel bars within active third- and fifth-order streams. Soil samples were collected in mid-March, and emergence from rhizome pieces and seeds was monitored under greenhouse conditions [24]. Liverleaf wintergreen did not emerge from vegetative propagules or seed in soil samples collected on burned or unburned quaking aspen stands in northeastern Alberta. Lightly and severely burned sites were sampled. The fire on severely burned sites consumed all aboveground vegetation and oxidized the top 2 to 4 inches (6-10 cm) of the organic soil layer. Light fires partially oxidized the top 0 to 0.8 inch (2 cm) of the organic layer, primarily mosses and litter. Unburned stands were over 120 years old [49].

Germination: The little information on liverleaf wintergreen seed germination comes from the study conducted by [4], which is presented in seed banking.

Seedling establishment/growth: No information is available on this topic.

Vegetative regeneration: Liverleaf wintergreen regenerates vegetatively by rhizomes. Researchers in south-central Alaska's Wrangell-St Elias National Park classified liverleaf wintergreen as a "guerilla" colonizer because daughter ramets typically occurred beyond the perimeter of the aboveground parent plant [10].

SITE CHARACTERISTICS:
Moist sites including coniferous forests, woodlands, meadows, streambanks, fens, bogs, and swamps all provide liverleaf wintergreen habitat [28,33,42,52,57,73].

In the Vancouver Forest Region of British Columbia, liverleaf wintergreen indicates "dry to moist, nutrient-medium" sites [37]. In seral shrub communities within the western redcedar-western hemlock forest type in northern Idaho, liverleaf wintergreen was most frequent on slopes over 60% and at the study area's northernmost latitudes. Liverleaf wintergreen was significantly associated (P<0.05) with northern slopes, soils with low potassium levels (60-300 lbs/acre), and dense stands with 40% to 80% canopy cover [55].

Climate: Cool moist climates are typical in liverleaf wintergreen habitats. In the McKinley River area of Alaska, liverleaf wintergreen is described in habitats that average 20.3 inches (515 mm) of precipitation/year, most of which comes in the summer. Average January and July temperatures are -2.2 F (-19 C) and 52.7 F (11.5 C), respectively, with maximum and minimum temperatures of 81 F (27 C) and -45 F (-43 C) reported [87]. Liverleaf wintergreen in coastal British Columbia experiences boreal, temperate, cool mesothermal climates [38]. Climate is humid, continental in lodgepole pine forests in Alberta's northern McLeod River Basin, where liverleaf wintergreen occurs. Here winters are cold, summers are cool, and freezing temperatures are possible any month. July and January temperatures average 58.8 F (14.9 C) and 6.8 F (-14 C), respectively, and annual precipitation averages 21.7 inches (550 mm) [9]. Weather records from the Priest River Experimental Station describe the climate for liverleaf wintergreen habitats in north Idaho's Selkirk Mountains. Annual precipitation is high, and nearly 75% falls as snow from October to April. The dormant season is long and cool, and the growing season is short, warm, and dry. The frost-free period averages 88 days [74]. A cool temperate climate prevails at Point Beach State Forests in Two Rivers, Wisconsin, where liverleaf wintergreen occurs. Based on a 24-year record, time between frosts averaged 62 days. An extreme low of -12 F (-24 C) occurred in January, and an extreme high of 88 F (31 C) was reached in June. Annual precipitation averaged 25 inches (635 mm), and most came in May, July, and November [85].

Elevation: Liverleaf wintergreen occupies higher elevations in the southern than in the northern part of its range.

Elevation tolerances for liverleaf wintergreen
State/region Elevation (feet)
California 300-10,000 [28,57]
California, southern 7,000-9,300 [56]
Colorado 6,500-12,000 [26,67]
not below 8,000, according to [5]
New Mexico 9,000-11,000 [52]
Nevada 5,800-8,000 [35]
Utah 5,495-10,520 [95]
Washington, Mount Rainier National Park 2,000-4,000 [70]
Intermountain West 5,050-10,500 [31]
Pacific Northwest "low" elevations to timberline [61]
Yukon up to 3,900 [33]

Soils: Liverleaf wintergreen occurs on a variety of substrate types, but soils are typically moist, acidic, and have thick litter or humus layers. In Manitoba, liverleaf wintergreen grew in "fresh" to very moist, clayey, loamy, silty, and sandy soils [96]. In northwestern Quebec, liverleaf wintergreen occurred only on mesic clay soils when boreal forests on clay and till surface deposits were compared [50].

In white fir-mixed conifer forests in the Sierra Nevada of California, liverleaf wintergreen was common on soils covered with a "heavy carpet of litter" [66]. In forests along the Tanana River of interior Alaska, liverleaf wintergreen occurred in open balsam poplar (Populus balsamifera) woodlands with a forest floor thickness of 2 to 4 inches (5-10 cm) and 225 to 350 g/m of leaf litter. Liverleaf wintergreen also grew in open black spruce (Picea mariana) forests with a floor thickness of 9.8 to 12 inches (25-30 cm), 30 to 100 g/m of leaf litter, and a 12- to 20-inch (30-50 cm)-deep organic layer [86]. In the McKinley River Area, liverleaf wintergreen was described in birch-willow shrublands on glacial outwash deposits where humus layers were up to 14 inches (35 cm) thick, and pH was less than 5.7 [87].

Liverleaf wintergreen occupied dry to wet sites within boreal conifer-hardwood forests of the Great Lakes region. Dry and wet soils averaged 161% and 365% dry-weight moisture-retaining capacity, respectively. Soil pH ranged from 4.5 to 4.9 [53]. In coastal British Columbia, liverleaf wintergreen is indicative of moderately dry, fresh, and nitrogen-medium soils. Moderately dry soils experience water deficits more than 1.5 but less than 3.5 months/year. When water needs exceed supply and soil-stored water is used, soils are considered fresh. Nitrogen-medium soils are those with an average of 54 kg of mineralizable nitrogen/ha [38].

SUCCESSIONAL STATUS:
Early seral deciduous woodlands and late-seral or climax coniferous forests provide liverleaf wintergreen habitat. In Glacier Bay, Alaska, liverleaf wintergreen occurs in the early succession of glaciated rock surfaces [8] and in open willow thickets, closed thickets, and Sitka spruce forests [7]. In Alberta, liverleaf wintergreen is a common understory species in balsam poplar and quaking aspen woodlands which, without fire or other top-killing disturbances, succeed to white spruce forests with liverleaf wintergreen remaining in the understory [54]. In Montana's Glacier National Park, liverleaf wintergreen was present in all but pioneer forests. Stands between 50 and 400 years old within the western redcedar-western hemlock forest type were sampled [15]. liverleaf wintergreen is often described in climax forests. It occurs in montane and subalpine forests on British Columbia's Mount Robson [6], climax western hemlock-Sitka spruce forests in southeastern Alaska [81], and in climax western redcedar-western hemlock-grand fir (Abies grandis) forests in Idaho's Bitterroot Mountains [45].

Shade tolerance: Liverleaf wintergreen tolerates both sun and shade conditions [38]. The degree of shade tolerated has been described as extreme [45]. Although sun and shade are tolerated, studies suggest that shady habitats may be preferred. Liverleaf wintergreen was significantly associated (P<0.001) with mesic, closed-canopy, mixed-conifer forests with thick litter layers and high soil moisture contents in the southern Sierra Nevada [60]. In northern Idaho, liverleaf wintergreen was significantly associated (P<0.05) with dense seral mixed-shrub stands with 40% to 80% canopy cover [55].

Floodplain/glacier outwash succession: Along floodplain chronosequences, liverleaf wintergreen is often present on early substrates with canopy vegetation and persists in dense climax forests. On the Tanana River floodplain in interior Alaska, liverleaf wintergreen appears approximately 25 to 30 years after silt bars form along the active river channel. This early seral community is characterized by open balsam poplar-dominated stands with a dense thinleaf alder (Alnus incana subsp. tenuifolia) understory. Liverleaf wintergreen remains in the understory in later, conifer-dominated stands [84,88]. Along a glacial outwash plain in Kenai Fjords National Park, Alaska, liverleaf wintergreen cover was greatest in late-seral forests dominated by Sitka spruce and mountain hemlock (Tsuga mertensiana). Liverleaf wintergreen was absent from early seral communities described as barren or with patchy vegetation dominated by balsam poplar and willow [27].

Grazing: While no study indicates that liverleaf wintergreen is consumed by herbivores, the following studies suggest that grazing in liverleaf wintergreen habitats may affect its abundance. Snowshoe hare and moose browsing were evaluated on enclosed and unprotected thinleaf alder-willow stands on the Tanana River floodplain. Liverleaf wintergreen abundance was lower on browsed than protected sites. Sites were protected for 7 years. Browsed plots had lower tree cover, soil moisture, and relative humidity and received more light and higher ground temperatures than unbrowsed plots [80]. In the Peace River region of British Columbia, liverleaf wintergreen cover was slightly greater in grazed quaking aspen stands. Liverleaf wintergreen cover was 1.5% on harvested and grazed plots, 1.2% on unharvested grazed plots, 0.5% on harvested ungrazed plots, and 1% on unharvested ungrazed plots. Harvesting occurred 12 years before vegetation sampling. Cattle grazed plots from early June to early July for 9 years and utilized about 75% of available forage. Grazing had not occurred for 3 years before vegetation sampling [40].

Logging: Results are inconsistent with respect to liverleaf wintergreen in logged stands. Some studies report that liverleaf wintergreen disappears from clearcut sites while others report a tolerance of clearcut conditions.

Liverleaf wintergreen occurred only in young mixed Douglas-fir-lodgepole pine forests in south-central British Columbia. Young stands were clearcut 17 years before the study. Other forests evaluated as part of the study were seed-tree harvested stands with 106- to 149-year-old Douglas-fir trees and unharvested stands with 70- to 133-year-old trees [79]. In the northern McLeod River Basin, liverleaf wintergreen occurred in 6-, 7-, 9-, 10-, and 12-year-old clearcuts and in mature lodgepole pine forests [9].

In northeastern British Columbia, liverleaf wintergreen was much more abundant in unlogged than logged stands in nearly 100-year-old quaking aspen woodlands [20]. In western Oregon and Washington, liverleaf wintergreen was often absent from harvested Douglas-fir forests with 15% or 40% tree retention [21]. Liverleaf wintergreen was eliminated in logged and burned stands in the same area. Before logging, forests were dominated by 120- to over 430-year-old Douglas-fir trees. Understory species presence was evaluated before logging and periodically for up to 28 years after the disturbances [22]. For more on this study, see Fire Effects.

There was liverleaf wintergreen turnover when individual plots were observed in clearcut quaking aspen-lodgepole pine stands; however, overall occurrence was not different in 3- and 20-year old clearcuts. Liverleaf wintergreen occurrence was monitored on 88 plots near Grande Prairie, Alberta. Forests were dominated by 62- to 82-foot (19-25 m)-tall quaking aspen before harvesting. Forests were about 20% lodgepole pine. Three years following harvest, liverleaf wintergreen occurred on 28 of 88 plots. On 5-year-old clearcuts, liverleaf wintergreen disappeared from 8 plots where it was previously detected and appeared on 3 new plots where it was not detected earlier. Liverleaf wintergreen was present on a total of 33 of the 5-year-old clearcut plots. Nine years after harvest, liverleaf wintergreen occurred on 3 new plots and was not detected on 16 plots that it had earlier occupied. Liverleaf wintergreen occurred on a total of 20 of the 9-year-old clearcut plots. On 20-year-old clearcuts, liverleaf wintergreen disappeared from 3 plots, appeared on 20 new plots, and was present on a total of 30 plots. It is possible that there was considerable liverleaf wintergreen mortality and regeneration on this site, but it is also possible that liverleaf wintergreen remained dormant in some years. Sampling techniques may have also affected results [77]. See Fire Effects for additional information on liverleaf wintergreen in the early succession of sites following canopy removal.

Other disturbances: The following studies suggest that liverleaf wintergreen tolerates some level of soil disturbance. These studies, however, suggest that the degree of soil disturbance tolerated and recovery time may be site dependent. Liverleaf wintergreen occurred on grizzly bear digs in alpine tundra in Wrangell-St Elias National Park. Digs were made in the hunt for arctic ground squirrels and involved a deep excavation of sod and mineral soil. Dig area ranged from 10 to 200 feet (1-20 m) [10]. Liverleaf wintergreen occurred in borrow pits and vehicle tracks but not on undisturbed sites along the Canol Road east of Macmillan Pass in the Northwest Territories. Disturbed and undisturbed sites were within the bog birch/star reindeer lichen (Betula glandulosa/Cladonia alpestris)-moss tundra habitat type. Borrow pits and vehicle tracks were created during pipeline construction and were abandoned 48 years before this study. Undisturbed sites had higher cover and abundance of woody plants than disturbed sites [25]. Liverleaf wintergreen had a strong negative correlation (r = -0.50) with moderate and severe levels of mechanical site disturbances in boreal forests of central and northeastern British Columbia. Liverleaf wintergreen abundance was greatest on undisturbed and/or low-severity disturbed sites [19].

SEASONAL DEVELOPMENT:
Liverleaf wintergreen begins producing flowers in June or July. Flowering times are apparently slightly later in the eastern part of its range.

Flowering dates for liverleaf wintergreen
State/region Flowering dates
California June-September for P. a. subsp. asarifolia [56,57];
June-July for P. a. subsp. bracteata [57]
Michigan usually 1st week in July [89]
Nevada July-September [35]
New Mexico July-August [52]
Washington,
Willamette, Mt Hood, Siuslaw National Forests
June-September [82]
Intermountain West June-September [30]
New England 21 June-23 July [68]
Northeastern United States July-August [13]

FIRE ECOLOGY

SPECIES: Pyrola asarifolia
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: To date (2007) there is little published information on liverleaf wintergreen's fire adaptations or responses. Liverleaf wintergreen is shallowly rooted [16,78], and plant survival may depend on depth of burn and degree of soil heating. Liverleaf wintergreen seedlings have not been described on burned sites, and general information on seedling establishment is lacking. Soil-stored seed survived temperatures of 210 F (100 C) for 1 hour under controlled conditions. For more on this study, see Heating effects on seed bank [4].

Fire regimes: Fires are common in mixed-conifer, boreal, and subalpine forests that provide liverleaf wintergreen habitat. Average fire-return intervals reported for these forests range from 23 to 258 years.

Larsen [47] indicates that a mix of fire severities is possible in boreal forests. Early spring fires that typically burn when humus layers are wet are often low severity and kill few perennial plants. Severe fires require dry, deep fuels. Consumption of the humus layer by severe fires results in more plant death. Mixed-severity fires are common in mixed stands because the deep fuels that accumulate under spruce and are generally lacking under quaking aspen canopies.

A review of fire ecology studies in northern Idaho forests provides the range of average fire-return intervals in forests where liverleaf wintergreen occurs. Moist, subalpine habitats at 5,000 to 6,500 feet (1,500-2,000 m) dominated by subalpine fir, western hemlock, and mountain hemlock burn in low- to moderate-severity fires on average every 150 years. Stand-replacing fires are less frequent than mixed-severity fires. In moderately moist to moist grand fir-dominated forests, the mixed-severity fire-return interval averages range from 29 to over 116 years. Stand-replacing fire-return intervals average 138 to 203 years. The range of averages is a result of means reported from different areas and different studies. In moderately moist to moist western hemlock and western redcedar forests, average stand-replacing fire-return intervals range from 138 to over 258 years, and mixed-severity fires occur on average every 29 to 48 years [69].

In Canada's boreal and subarctic regions, summers are warm and dry, periods of sunlight are long, and the high cover of lichens and mosses dries readily. These factors produce readily burned surface fuels. In the Fort Simpson study area in the Northwest Territories where liverleaf wintergreen occurs, researchers sampled 21 stands, dated 43 fires, and found that the interval between fires was 6 to 100 years. The average fire-return interval was 23 years 10 (SD). Sites were dominated by mixed woodlands and pine (Pinus spp.) forests. Lightning was the major fire cause [65].

Mixed-conifer forests of the Teakettle Experimental Forest in the southern Sierra Nevada averaged 12 to 17 years between fires before 1865; since 1865, however, only 2 small fires have burned (references cited in [60]).

The following table provides fire-return intervals for plant communities where liverleaf wintergreen occurs. This list may not be inclusive for all plant communities in which liverleaf wintergreen occurs. Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".

Fire regime information on vegetation communities in which liverleaf wintergreen may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models [43]. These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the .pdf file linked from the name of each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.
Pacific Northwest California Southwest Great Basin Northern Rockies
Northern Great Plains Great Lakes Northeast    
Pacific Northwest
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northwest Forested
Sitka spruce-western hemlock Replacement 100% 700 300 >1,000
Douglas-fir (Willamette Valley foothills) Replacement 18% 150 100 400
Mixed 29% 90 40 150
Surface or low 53% 50 20 80
Douglas-fir-western hemlock (dry mesic) Replacement 25% 300 250 500
Mixed 75% 100 50 150
Douglas-fir-western hemlock (wet mesic) Replacement 71% 400    
Mixed 29% >1,000    
Mixed conifer (southwestern Oregon) Replacement 4% 400    
Mixed 29% 50    
Surface or low 67% 22    
Mountain hemlock Replacement 93% 750 500 >1,000
Mixed 7% >1,000    
Subalpine fir Replacement 81% 185 150 300
Mixed 19% 800 500 >1,000
Mixed conifer (eastside mesic) Replacement 35% 200    
Mixed 47% 150    
Surface or low 18% 400    
Spruce-fir Replacement 84% 135 80 270
Mixed 16% 700 285 >1,000
California
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
California Forested
Mixed conifer (North Slopes) Replacement 5% 250    
Mixed 7% 200    
Surface or low 88% 15 10 40
Mixed conifer (South Slopes) Replacement 4% 200    
Mixed 16% 50    
Surface or low 80% 10    
Aspen with conifer Replacement 24% 155 50 300
Mixed 15% 240    
Surface or low 61% 60    
Interior white fir (northeastern California) Replacement 47% 145    
Mixed 32% 210    
Surface or low 21% 325    
Red fir-white fir Replacement 13% 200 125 500
Mixed 36% 70    
Surface or low 51% 50 15 50
Sierra Nevada lodgepole pine (cold wet upper montane) Replacement 23% 150 37 764
Mixed 70% 50    
Surface or low 7% 500    
Southwest
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Southwest Forested
Riparian forest with conifers Replacement 100% 435 300 550
Southwest mixed conifer (cool, moist with aspen) Replacement 29% 200 80 200
Mixed 35% 165 35  
Surface or low 36% 160 10  
Aspen with spruce-fir Replacement 38% 75 40 90
Mixed 38% 75 40  
Surface or low 23% 125 30 250
Lodgepole pine (Central Rocky Mountains, infrequent fire) Replacement 82% 300 250 500
Surface or low 18% >1,000 >1,000 >1,000
Spruce-fir Replacement 96% 210 150  
Mixed 4% >1,000 35 >1,000
Great Basin
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Great Basin Forested
Great Basin Douglas-fir (dry) Replacement 12% 90   600
Mixed 14% 76 45  
Surface or low 75% 14 10 50
Aspen with conifer (low to midelevation) Replacement 53% 61 20  
Mixed 24% 137 10  
Surface or low 23% 143 10  
Douglas-fir (warm mesic interior) Replacement 28% 170 80 400
Mixed 72% 65 50 250
Aspen with conifer (high elevation) Replacement 47% 76 40  
Mixed 18% 196 10  
Surface or low 35% 100 10  
Spruce-fir-pine (subalpine) Replacement 98% 217 75 300
Mixed 2% >1,000    
Aspen with spruce-fir Replacement 38% 75 40 90
Mixed 38% 75 40  
Surface or low 23% 125 30 250
Northern Rockies
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northern Rockies Forested
Western redcedar Replacement 87% 385 75 >1,000
Mixed 13% >1,000 25  
Douglas-fir (xeric interior) Replacement 12% 165 100 300
Mixed 19% 100 30 100
Surface or low 69% 28 15 40
Douglas-fir (warm mesic interior) Replacement 28% 170 80 400
Mixed 72% 65 50 250
Douglas-fir (cold) Replacement 31% 145 75 250
Mixed 69% 65 35 150
Grand fir-Douglas-fir-western larch mix Replacement 29% 150 100 200
Mixed 71% 60 3 75
Mixed conifer-upland western redcedar-western hemlock Replacement 67% 225 150 300
Mixed 33% 450 35 500
Western larch-lodgepole pine-Douglas-fir Replacement 33% 200 50 250
Mixed 67% 100 20 140
Grand fir-lodgepole pine-larch-Douglas-fir Replacement 31% 220 50 250
Mixed 69% 100 35 150
Persistent lodgepole pine Replacement 89% 450 300 600
Mixed 11% >1,000    
Lower subalpine lodgepole pine Replacement 73% 170 50 200
Mixed 27% 450 40 500
Lower subalpine (Wyoming and Central Rockies) Replacement 100% 175 30 300
Upper subalpine spruce-fir (Central Rockies) Replacement 100% 300 100 600
Northern Great Plains
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northern Plains Woodland
Northern Great Plains wooded draws and ravines Replacement 38% 45 30 100
Mixed 18% 94    
Surface or low 43% 40 10  
Great Lakes
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Great Lakes Forested
Great Lakes floodplain forest
Mixed 7% 833    
Surface or low 93% 61    
Great Lakes spruce-fir Replacement 100% 85 50 200
Minnesota spruce-fir (adjacent to Lake Superior and Drift and Lake Plain) Replacement 21% 300    
Surface or low 79% 80    
Northeast
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northeast Forested
Northeast spruce-fir forest Replacement 100% 265 150 300
*Fire Severities: Replacement=Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Surface or low=Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area.
Mixed=Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects [23,44].

POSTFIRE REGENERATION STRATEGY [75]:
Rhizomatous herb, rhizome in soil

FIRE EFFECTS

SPECIES: Pyrola asarifolia
IMMEDIATE FIRE EFFECT ON PLANT:
Liverleaf wintergreen is top-killed if not entirely killed by fire.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
Liverleaf wintergreen is shallowly rooted [16,78], and survival may depend on depend on depth of burn and degree of soil heating.

PLANT RESPONSE TO FIRE:
There are reports of liverleaf wintergreen surviving fire through rhizome sprouting [51], and there are reports of liverleaf wintergreen being killed by fire [76]. Liverleaf wintergreen seedlings have not been described on burned sites, and general information on seedling establishment is lacking. Soil-stored seed survived temperatures of 210 F (100 C) for 1 hour under controlled conditions. For more on this study, see Heating effects on seed bank [4].

Liverleaf wintergreen survival is likely dependent on depth of burn and soil temperatures produced. Liverleaf wintergreen's small size and infrequency in most habitats suggests that general plot or site descriptions of fire severity may not capture microsite differences that are likely important to liverleaf wintergreen survival.

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
It is nearly impossible to describe a typical liverleaf wintergreen response to fire. Sometimes liverleaf wintergreen is absent from burned sites; sometimes abundance is lower on burned than unburned sites; sometimes abundance is greater on burned than unburned sites. Some studies suggest that high-severity fires kill liverleaf wintergreen [71,91,92], and other studies report the highest cover of liverleaf wintergreen on sites burned in high-severity fires [49]. As suggested earlier, liverleaf wintergreen rarely occurs with high cover or frequency in any habitat, and likely sampling effects, microsite burn conditions, and the postfire growing environment affect liverleaf wintergreen's postfire response.

Researchers classified liverleaf wintergreen as a "survivor" after observing the first 15 years of postfire regeneration following 3 wildfires in northern Idaho. All fires were stand replacing and reduced organic soil to mineral ash [51]. Liverleaf wintergreen was classified as a "nonsurvivor" after monitoring the early postfire succession after the Sundance Fire in the Rocky Mountains of northern Idaho and northwestern Montana. The Sundance Fire was "high intensity" and burned with "firestorm conditions" in the western redcedar-western hemlock forest type [76].

Heating effects on seed bank: The following study suggests that liverleaf wintergreen seed can survive temperatures as high as 210 F (100 C) for at least 1 hour. Soil samples were collected from burned and unburned tufted hairgrass-sedge meadow sites in the Greater Yellowstone Ecosystem of Montana and Wyoming. No seedlings emerged from burned sites. Burned soil was collected in areas with complete overstory removal but not in areas of smoldering described as "deep ash ghosts of burned downfall". The density of liverleaf wintergreen seedlings that emerged from seed in unburned tufted hairgrass meadows was 53 seedlings/m. Soil samples had been cleaned of vegetative propagules. Seedlings also emerged from heat-treated unburned soils. Unburned soil samples treated for 1 hour of oven heating at 120 F (50 C), 210 F (100 C), and 300 F (150 C) had 106 seedlings/m, 27 seedlings/m, and 0 seedlings/m emerge, respectively [4].

Absence from burned sites: Several studies report no liverleaf wintergreen on burned sites, not all of which burned in severe fires. Liverleaf wintergreen was absent from 1-year-old moderately and severely burned sites and 43-year-old burned sites along Jackson Lake in Grand Teton National Park, Wyoming. The frequency of liverleaf wintergreen in unburned Engelmann spruce (Picea engelmannii)-subalpine fir forest sites was 13% [2]. Liverleaf wintergreen was eliminated from logged and burned Douglas-fir forests in western Oregon and Washington. Before logging, forests were dominated by 120- to over 430-year-old trees. Understory species presence was evaluated before logging and periodically for up to 28 years after disturbances [22]. There may have been delayed mortality of liverleaf wintergreen on logged and slash burned Douglas-fir forests in Oregon's western Cascade Range. Before logging, liverleaf wintergreen cover was 0.1%, and frequency was 1.8% in old-growth (300-500 years old) stands. In the first postlogging year, liverleaf wintergreen cover was less than 0.05%, and frequency was 0.4%. In the 1st, 2nd, 3rd, and 4th years following slash burning, liverleaf wintergreen occurred only in trace amounts. In the 5th year after logging and slash burning, liverleaf wintergreen was not present on burned sites [11].

Present on burned sites: Liverleaf wintergreen abundance was not different on burned and unburned subalpine sites visited 10 years after fire in Alberta. There were no significant (P<0.05) differences in liverleaf wintergreen cover on 10-year-old burned and adjacent unburned subalpine white spruce-lodgepole pine forests on 2 burned sites. The fire near Banff National Park burned in late August and early September, spread at a daily average speed of 3.4 to 6.7 m/min. The fire near Jasper National Park burned in October, had a maximum spread rate of 26.8 m/min, and an average spread rate of 3.4 m/min [3]. In boreal mixed woods of southeastern Manitoba, sites burned 10 to 13 years earlier in a crown fire had 0.2% cover and 10% frequency of liverleaf wintergreen. Sites logged 10 to 14 years earlier had 0.4% cover and 11% frequency of liverleaf wintergreen [36].

Liverleaf wintergreen frequency decreased but cover increased 7 years after a June prescribed fire in spruce beetle-damaged white spruce forests in Alaska's Chugach National Forest. Prior to the fire, liverleaf wintergreen frequency was 24% and cover 5%. Seven years after the fire, which exposed the mineral soil in some areas, liverleaf wintergreen frequency was 6% and cover was 13%. Increased cover and decreased frequency could be explained by fewer large-sized plants after the fire [32].

Severely burned sites: Some studies report no liverleaf wintergreen on severely burned sites, but others report liverleaf wintergreen persistence on severely burned sites. Liverleaf wintergreen did not occur on unburned plots or plots burned in a "hot" prescribed fire in western larch (Larix occidentalis)-Douglas-fir forests in Montana's Lubrecht Experimental Forest. Spring and fall prescribed fires were evaluated 3 years later and described as "light", "medium", and "hot" burns [71,72]. Liverleaf wintergreen was absent from plots unburned for 70 years and from plots burned in "hot" fires that consumed litter, exposed mineral soil, and produced surface temperatures above 570 F (300 C). Liverleaf wintergreen averaged 1% cover 3 years after "medium" fires that consumed 50% of litter and duff and produced surface temperatures of 390 to 570 F (200-300 C). Cover averaged 0.5% on "light" burns where surface temperatures were less than 360 F (180 C) at the time of the fire, and less than 50% of litter was consumed [71].

In southeastern Manitoba, liverleaf wintergreen was present on scorched, "lightly" burned, 10-year-old burned, and mature unburned boreal mixed woods but was absent from severely burned sites. The Black River wildfire burned in early May 1999, and postfire vegetation was sampled for up to 4 years after fire. Fire severity was determined by assessing depth of burn. Scorching fires did not burn or just partially burned the litter layer. Light fires burned the litter layer but consumed little or no duff. Severe fires consumed the forest floor completely. Liverleaf wintergreen averaged 0.1% and 6% cover and frequency, respectively, on scorched sites. Cover and frequency averaged <0.1% and 3%, respectively, on lightly burned sites [91,92].

Liverleaf wintergreen cover was greatest on severely burned sites when unburned, "lightly" burned, and severely burned sites were compared 2 years following a spring fire in quaking aspen stands in northeastern Alberta. Liverleaf wintergreen cover averaged 1% on severely burned, 0.5% on "lightly" burned, and 0.3% on unburned sites. Unburned stands were over 120 years old. The researcher visually assessed fire severity. Severely burned sites had all aboveground vegetation consumed, and the top 2 to 4 inches (6-10 cm) of the organic layer oxidized. Light fires partially oxidized the top 0 to 0.8 inch (2 cm) of the organic layer of primarily mosses and litter. Liverleaf wintergreen did not emerge from vegetative propagules or seed in soil samples collected on burned or unburned sites [49]. Liverleaf wintergreen was present on 11-year-old burned stands but absent from unburned sites in a mixed-conifer forest in northwestern Oregon. The fire was described as severe, and unburned stands were an estimated 300 years old [58].

Repeatedly burned sites: Frequency of liverleaf wintergreen on unburned sites and sites burned more than once was much lower than once burned, once logged, and once logged and burned sites in seral shrub communities within the western redcedar-western hemlock forest type of northern Idaho. Sampled stands were 2 to 60 years old. A variety of sites was sampled, making it difficult to determine which affected liverleaf wintergreen frequency most: site conditions, disturbance type, or time since disturbance. A description of the sites where liverleaf wintergreen was most frequent is available in Site Characteristics. The table below summarizes study results [55].

Overstory canopy cover and liverleaf wintergreen frequency on logged, logged and burned, and burned stands
Disturbance None Logged,
unburned
Logged,
pile burned
Single fire ≥2 fires in 30 years
Overstory canopy cover (%) 57% 41% 40% 20% 28%
Liverleaf wintergreen frequency (%) 5% 18% 15% 12% 5%

FIRE MANAGEMENT CONSIDERATIONS:
The variable liverleaf wintergreen fire response makes it difficult to make recommendations about fire use and fire management in its habitats. More specific information regarding postfire regeneration strategies, root and rhizome depths, and seed heat tolerance may improve the predictability of liverleaf wintergreen recovery on burned sites.

MANAGEMENT CONSIDERATIONS

SPECIES: Pyrola asarifolia
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Use of liverleaf wintergreen by wildlife or livestock was not reported in the available literature (2007).

Palatability/nutritional value: No information is available on this topic.

Cover value: Liverleaf wintergreen is a small plant that likely provides cover for only arthropods.

VALUE FOR REHABILITATION OF DISTURBED SITES:
No information is available on this topic.

OTHER USES:
Native people of the Pacific Northwest used a liverleaf wintergreen poultice for sores and swellings [61].

OTHER MANAGEMENT CONSIDERATIONS:
Spruce cone rust (Chrysomyxa pirolata) uses wintergreens (Pyrola spp.) as hosts. Spruce cone rust was found on liverleaf wintergreen in an Engelmann spruce-subalpine fir stand in central Utah [59].

On the Teakettle Experimental Forest, liverleaf wintergreen was significantly associated (P<0.001) with mixed-conifer forests with closed canopies, a thick litter layer, and high soil moisture content. Tree species in these forests included white fir, California black oak (Quercus kelloggii), sugar pine (Pinus lambertiana), Jeffery pine (P. jeffreyi), and incense-cedar (Calocedrus decurrens). Liverleaf wintergreen may be an indicator species for these forests and site conditions [60].

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